Microsurgical procedures frequently require precision cutting and/or removing of various body tissues. For example, certain ophthalmic surgical procedures require cutting and removing portions of the vitreous humor, a transparent jelly-like material that fills the posterior segment of the eye. The vitreous humor, or vitreous, is composed of numerous microscopic fibrils that are often attached to the retina. Therefore, cutting and removing the vitreous must be done with great care to avoid traction on the retina, the separation of the retina from the choroid, a retinal tear, or, in the worst case, cutting and removal of the retina itself. In particular, delicate operations such as mobile tissue management (e.g., cutting and removal of vitreous near a detached portion of the retina or a retinal tear), vitreous base dissection, and cutting and removal of membranes are particularly difficult.
Conventional vitrectomy probes typically include a hollow outer cutting member, a hollow inner cutting member arranged coaxially with and movably disposed within the hollow outer cutting member, and a port formed on a side wall of the outer cutting member. Vitreous humor and/or membranes are aspirated into the open port, and the inner member is actuated, closing the port. As the port closes, cutting surfaces on both the inner and outer cutting members cooperate to cut the vitreous and/or membranes. The cut tissue is then aspirated away through the inner cutting member. Because the port is formed on the side wall of the outer cutting member, the conventional vitrectomy probe may require the surgeon to maneuver the conventional vitrectomy probe in order to engage a tissue. Further, the port to tip distance (PTTD) of a conventional vitrectomy probe is typically about 0.009″-0.015″. The PTTD should be reduced (e.g., ideally at 0″) to improve surgical precision.